Karyotypes of Five Species of Coral Snakes (Micrurus)

Abstract

There are more than 50 species of coral snakes classified in the genera Micrurus and Micruroides (Roze, 1982). The evolutionary relationships within this group, as well as between coral snakes and Old World elapids, have been studied only to a partial extent. Most studies have been based on morphological analyses (e.g., Savage and Vial, 1973; Roze, 1982), although immunochemical comparisons of serum albumins have also been used (Cadle and Sarich, 1981; Cadle and Gorman, 1981). Chromosome studies have shown extensive karyotype variation between elapid species (Singh, 1972a; Singh, 1974; Graham, 1977; Gutierrez and Bolafios, 1979; Gorman, 1981). Thus, karyology may become a useful tool in understanding the phylogenetic relationships among elapid snakes in general, and within coral snakes in particular. Karyotypes of five species of Micrurus have been reported: M. lemniscatus (Becak and Becak, 1969), M. fulvius (Graham, 1977), M. nigrocinctus, M. alleni, and M. mipartitus (Gutierrez and Bolafios, 1979, 1981). In this work we describe the karyotypes of five additional species of Micrurus: M. elegans, M. diastema, M. hippocrepis, M. browni, and M. surinamensis. To obtain the karyotypes, the method of Gutierrez and Bolafios (1979), based on the simultaneous injection of phytohemagglutinin and colchicine, was used. From each species, at least 30 mitotic figures were studied to determine the diploid number; from these, four were selected and photographed to prepare idiograms. Chromosomes were classified using the nomenclature proposed by Levan et al. (1964). The Nombre Fondamentale (NF) was defined as the number of arms of the macrochromosomes. The specimens used in this study were collected in the following locations: M. browni, two males from Volcan de Agua, Guatemala; M. diastema sapperi, one male from Izabal, Guatemala; M. diastema apiatus, one female from Purulha, Baja Verapaz, Guatemala; M. elegans, three males from Purulha, Baja Verapaz, Guatemala; and M. surinamensis, one male from Guyanas. All of the specimens studied are kept at the Museum of Zoology of the Universidad de Costa Rica. In M. elegans the diploid number is 30, with 16 macro and 14 microchromosomes and with an NF of